Confidence interval for mean using normal distribution.
A market research company surveys individuals to determine how much money they spend each year on clothing. They sample 30 individuals and the sample mean is $1287 with a sample standard deviation of 632.
Required:
1.estimation the population expenditure on clothing with 95% confidence.
2. Estimate the population expenditure on clothing with 99% confidence.
3. Explain the difference between your results in 1 and 2.
If the population mean was $1047 in the previous year, does the evidence suggest that expenditure this year has significantly changed?